The present invention relates to a yarn winding bobbin adapted for use on continuous winding machines and which has a yarn catching slot of novel construction.
EP 524,545 and corresponding U.S. Pat. No. 5,248,111 disclose a yarn winding bobbin having a slot designed to catch the running yarn during the yarn transfer operation of a continuous winding machine. More particularly, the running yarn is laid on the winding bobbin in such a way that the direction of movement of the yarn corresponds to the direction of movement of the surface of the winding bobbin. This so-called "same direction catching" has the advantage that the yarn being delivered to the full package does not slip at the instant when the yarn is laid on to the empty winding bobbin, note EP 374 536 and corresponding U.S. Pat. No. 5,029,762. For this purpose, the winding bobbin has a catching slot, lying in a normal plane, which consists of a through opening and a clamping slot following in the circumferential direction. Fashioned on one of the side flanks of the through opening is a catching tongue which catches the yarn running on a secant of the inner circumference when the winding bobbin is rotated further, thereby preventing the yarn from rising radially out of the catching slot. As movement progresses, the yarn is deflected by the catching tongue, so that the yarn is drawn into the clamping slot located at the yarn delivery end of the through opening.
Since, in the case of same direction catching, no relative movement occurs between the yarn and the winding bobbin, the yarn can only be drawn into the clamping slot by being wrapped on the catching tongue. It has been shown that, particularly in the case of BCF yarns, which normally lie within the titer range of 500 to 4,000 dtex, the yarn is not drawn into the clamping slot. Due to the high inherent dynamic forces acting on the yarn, the yarn repeatedly becomes unwrapped and rises radially out of the catching slot.
An object of the invention, therefore, is to further develop a winding bobbin of the type referred to in such a way that even yarns with larger titers are reliably caught.